Study on the deacetylation of hemicelluloses during the hydrothermal processing of Eucalyptus wood

Eucalyptus globulus wood samples were subjected to hydrothermal treatments at a liquor to wood ratio in the range 6-10 g/g and temperatures from 145 up to 190 degreesC. The effects caused by hydrothermolysis included extractive removal, hemicellulose degradation and deacetylation of both hemicelluloses and acetylated oligosaccharides. An analytical procedure based on the determination of the xylose and acetic acid contained in liquors before and after a quantitative posthydrolysis allowed the determination of acetyl groups bound to residual xylan and oligosaccharides. Since hydronium ions (the catalytic species involved in the degradation of the polymeric fractions of biomass) are mainly generated from acetic acid, special attention was paid to interpretate the time course of acetyl groups hydrolysis from both xylan and xylan-degradation products, and their interrelationship with the concentration of acetic acid is established.